Porcelain Sink Repair

I have been asked to repair a "chip" in a procelain sink. Does anyone have any experience in this area? Ideas on what material to use, application techniques and things to look out for would be appreciated.

If you want it to look "good" call a professional refinisher. If you just want to cover up the chip and do not care what it looks like, use a repair kit from Home Depot or a similar store. However for most sinks a new sink is almost easier and cheaper than a repair.